From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Bench tests conducted on paraffin wax filled coils to assess their performance and temperature effects.
| Identifier | ExFiles\Box 69\1\ scan0155 | |
| Date | 29th September 1928 | |
| EFC. WD.{Mr Wood/Mr Whitehead}14. 29.9.28. PARAFFIN WAX FILLED COILS. We have now conducted bench tests on two coils, one wound and insulated with standard oiled paper and the other insulated with paraffin waxed paper, designated respectively WFl and PWFl, both being finer primary coils. Each coil was immersed in paraffin wax in its case by Mr. Brock's Dept. Bench tests on these two coils shewed that they remained slightly cooler than similar coils without the paraffin wax, but the H.T. sparking performance was poor even under normal conditions, and at 100°C, misfiring was bad at 12 volts on the spark gaps. We suspected that the wax, when the coil was immersed, had been subjected to too high a temperature, allowing cracking to take place which would cause slight carbonisation. The wax was therefore melted and emptied out of each coil case, and it was noted that the wax was quite discoloured brown instead of white. The PWFl coil was also found to be wrapped round with cotton tape and this was removed as it was considered to be contributory to the secondary weakness. Each coil was then tested again at 100°C. and an improvement noted, the coils now sparking quite regularly on the gaps. The coils were then immersed in pure paraffin wax which was not allowed to attain a high temperature, in the lab., and again tested at 100°C. when no appreciable difference was observed in the sparking performance, as compared with the performance without the wax. We then conducted leakage tests on pure paraffin wax :- (a) After it had been melted and not subjected to more than 150° (b) After subjection to a high temperature of 275°C. and we found that in the case of (a) no leakage was observed and the wax remained white as when new, but in the case of (b) the wax became discoloured brown and a conductance of .003 microhmos was obtained. We therefore conclude that paraffin wax filled coils remain slightly cooler than standard and do not appear to be any the worse electrically providing the wax is pure and not taken to a temperature higher than 150°C. | ||